Eye-Protection Device Having Dual High Voltage Switching

ABSTRACT

An auto darkening eye protection device comprising a shutter assembly and a control circuit. The shutter assembly is adjustable between a light state and a dark state. The control circuit comprises a sensing circuit, a weld detect circuit, a positive voltage generator, and a negative voltage generator. The sensing circuit senses incident light and provides an output indicative of the incident light. The weld detect circuit receives the output of the sensing circuit, and enables a dark state drive signal to be delivered to the shutter assembly. The positive and negative voltage generators output the dark state drive signal to the shutter assembly to switch the shutter assembly from the light state to the dark state upon enablement by the weld detect circuit. The dark state drive signal includes a high voltage pulse followed by a stable AC waveform. The high voltage pulse is formed by a positive voltage signal and a negative voltage signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present patent application is a divisional patent application ofU.S. Ser. No. 11/401,353, filed Apr. 10, 2006, now U.S. Pat. No.7,446,292, which is a continuation of U.S. Ser. No. 10/915,929, filed onAug. 11, 2004, now U.S. Pat. No. 7,026,593, which claims priority to theprovisional patent application identified by the U.S. Ser. No.60/494,280, which was filed on Aug. 11, 2003, the entire contents ofwhich are hereby expressly incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an eye protection device constructed inaccordance with the present invention.

FIG. 2 is a schematic diagram of one embodiment of a control circuitconstructed in accordance with the present invention for controlling ashutter assembly.

FIG. 3 is a schematic diagram of another embodiment of a control circuitconstructed in accordance with the present invention for controlling ashutter assembly.

FIG. 4 is a graph illustrating a positive voltage signal and a negativevoltage signal in accordance with the present invention.

FIG. 5 is a front perspective view of the eye protection device.

FIG. 6 is a rear perspective view of the eye protection device.

FIG. 7 is a rear elevational view of the eye protection device.

FIG. 8 is a side elevational view of the eye protection device.

FIG. 9 is a front elevational view of the eye protection device.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and in particular to FIG. 1, showntherein and designated by the reference numeral 10 is an eye protectiondevice constructed in accordance with the present invention. In general,the eye protection device 10 is designed to automatically darken in thepresence of an intense light, such as a welding arc. The eye protectiondevice 10 is preferably adapted to be worn by an individual. Forexample, the eye protection device 10 can be implemented in the form ofa cassette 11 (FIGS. 5-9) suitable for mounting in a welding helmet (notshown).

The eye protection device 10 is provided with a control circuit 12, anda shutter assembly 14. The shutter assembly 14 is an auto-darkeningfilter capable of being driven between a clear state and a dark state.In the clear state, an individual can see through the shutter assembly14 under ambient light conditions. In the dark state, the shutterassembly 14 becomes opaque so that the individual can comfortably seethrough the shutter assembly 14 in the presence of an intense light,such as a welding arc.

The switching speed of the eye protection device 10 is an importantperformance attribute of the eye protection device 10. As will be wellunderstood by those skilled in the art, the switching speed is the timeperiod for switching the shutter assembly 14 from the clear state to thedark state. As will be discussed in more detail below, in accordancewith the present invention, a dark state drive signal having a highvoltage, e.g. V, is provided to the shutter assembly 14 to enhance theswitching speed of the shutter assembly 14. The shutter assembly 14 ispreferably a liquid crystal display, such as a twisted nematic liquidcrystal display.

The control circuit 12 senses the intense light and outputs the darkstate drive signal to the shutter assembly 14 to cause the shutterassembly 14 to switch from the light state to the dark state. If thecontrol circuit 12 senses that no welding arc is present, the controlcircuit 12 will cause a “light state” drive signal to be delivered tothe shutter assembly 14.

In general, the control circuit 12 is provided with a power supply 16, asensor circuit 24, a weld detect circuit 28, a positive voltage timer32, a negative voltage timer 36, a positive voltage generator 40, anegative voltage generator 44, a delay circuit 48, and an oscillatorcircuit 52.

The power supply 16 includes a battery power supply 60, and a solarpower supply 64. The solar power supply 64 provides electrical power tothe sensor circuit 24 via a power line 68. The battery power supply 60provides electrical power to control circuit 12 via a power line 74.

The battery power supply 60 can be provided with any suitable voltage soas to supply power to the control circuit 12. For example, the batterypower supply 60 can be provided with a voltage in a range from about 2.0V to about 6.5 V. In one embodiment, such as depicted in FIG. 1, thepower supply 16 can further include a reference generator 75, whereinthe battery power supply 60 provides electrical power to the referencegenerator 75 so that the reference generator 75 can provide at least onepositive reference voltage and at least one negative reference voltagefor the control circuit 12. The reference voltages generated by thereference generator 75 are also generally higher in magnitude than thevoltage of the battery power supply 60. Since the reference generator 75provides higher magnitude positive and negative reference voltages, thebattery power supply 60 can be provided with a single lower voltage,thus reducing the cost of the battery power supply 60. In one preferredembodiment, the battery power supply 60 has about +3 Volts, and thereference generator 75 generates reference voltages of about +6 Voltsand −6 Volts. Although the control circuit 12 is shown in FIG. 2 asbeing provided with the reference generator 75, one of ordinary skill inthe art would recognize that the battery power supply 60 can be providedwith voltages so as to provide positive and negative reference voltagesfor the control circuit 12, thus eliminating the need for the referencegenerator 75.

In a preferred embodiment depicted in FIG. 2, the reference generator 75of the control circuit 12 is a charge pump which converts an essentiallysquare waveform output from the oscillator circuit 52 to the desired DCreference voltages (e.g. +6V and −6V) for other elements of the controlcircuit 12, such as for example, the weld detect circuit 28, thepositive voltage generator 40, and the negative voltage generator 44.Charge pumps are well known by those of ordinary skill in the art,therefore no further discussion of their operation is deemed necessary.

In one embodiment, as depicted for example in FIG. 2, the referencegenerator 75 includes capacitors (as designated by the referencenumerals C3, C4, C6, C7, C8, C17, and C23), diodes (as designated by thereference numerals D1, D2, and D4), and inverters (as designated by thereference numerals U6A and U6B). Another embodiment of a referencegenerator is shown in FIG. 3 and is designated therein by referencenumeral 75 a. The reference generator 75 a is similar to the referencegenerator 75 shown in FIG. 2, except that the reference generator 75 aincludes another capacitor C18 a, and the value of capacitor C23 hasbeen increased, so as to further stabilize the reference voltagesprovided by the reference generator 75 a.

In one preferred embodiment, the power supply 16 is also provided with acharging circuit 76 receiving output from the solar power supply 64 tocharge the battery power supply 60 when the solar power supply 64generates power above the voltage of the battery power supply 60,thereby extending the life of the battery power supply 60. In oneembodiment the charging circuit 76 includes at least one diode, asdesignated by the reference numeral D3.

To further extend the life of the battery power supply 60, in onepreferred embodiment, the solar power supply 64 also provides electricalpower to a power conservation circuit 78 via line 68, such as shown inFIG. 2, wherein the power conservation circuit 78 is formed by resistorsR5, R7, R12, and transistor Q1. When the solar power supply 64 is leftunexposed to incident light, i.e., is not providing electrical power,the power conservation circuit conserves the power of the battery powersupply 60 by effectively turning off the oscillator circuit 52, and thusthe reference voltages for the control circuit 12. For example, when thewelding helmet and/or cassette is laid down or put away in storage andnot in use, then the output of the solar power supply 64 will be low andthe reset of the oscillator circuit 52 will be high, causing theoscillator circuit 52 to only output low signals so as to prevent theoscillator circuit 52 from outputting the oscillating signals. Sincethere is no oscillating signals output by the oscillator circuit 52, noreference voltages will be generated by the reference generator 75,thereby effectively turning off the weld detect circuit 28, positivevoltage generator 40, and negative voltage generator 44 of the controlcircuit 12. As such, the power of the battery power supply 60 isconserved.

The sensor circuit 24 of control circuit 12 detects the presence oflight and outputs a sensor output signal representative of the level oflight detected. As shown in FIG. 1, the sensor output signal isoutputted to the weld detect circuit 28 via a signal path 80. The welddetect circuit 28 enables the drive signal that will be delivered to theshutter assembly 14. In general, if the sensor output signal indicatesto the weld detect circuit 28 that an intense light, such as a weldingarc is present, the weld detect circuit 28 will cause a dark state drivesignal to be delivered to the shutter assembly 14. If the sensor outputsignal indicates to the weld detect circuit 28 that no welding arc ispresent, the weld detect circuit 28 will cause a “light state” drivesignal to be delivered to the shutter assembly 14.

The dark state drive signal is provided with two components; a highvoltage pulse followed by a stable AC waveform. The high voltage pulsequickly drives the shutter assembly 14 from the light state to the darkstate. The stable AC waveform maintains the shutter assembly 14 in thedark state. The high voltage pulse preferably has a voltage in a rangefrom about 15 V to about 120 V, and a time period from about 10microseconds to about 100 milliseconds. In general, the voltage of thehigh voltage pulse will depend on the maximum voltage ratings of thecomponents utilized to implement the control circuit 12. In onepreferred embodiment, the voltage of the high voltage pulse is about 30V, and the time period of the high voltage pulse is about 10 ms.

As shown in FIG. 4, the high voltage pulse is formed by a positivevoltage signal (referenced to ground) synchronized with a negativevoltage signal (referenced to ground). The positive and negative voltagesignals are labeled in FIG. 4 with the designations “PVS” and “NVS”. Inother words, the leading edges of the positive voltage signal and thenegative voltage signals are synchronized. The shutter assembly 14 doesnot have a ground reference, and therefore, does not differentiatepositive or negative. The voltage of the high voltage pulse in the darkstate drive signal is thus the difference between the positive voltagesignal and the negative voltage signal. For example, if the positivevoltage signal has an amplitude of +18 Volts, and the negative voltagesignal has an amplitude of −12 Volts, the voltage of the high voltagepulse would be +18 V−(−12 V)=+30 Volts.

The positive voltage signal is produced by the positive voltage timer 32and the positive voltage generator 40. The negative voltage signal isproduced by the negative voltage timer 36 and the negative voltagegenerator 44. The positive voltage timer 32 sets the time period of thepositive voltage signal. The positive voltage generator 40 produces theamplitude of the positive voltage signal. Likewise, the negative voltagetimer 36 sets the time period of the negative voltage signal. Thenegative voltage generator44 produces the amplitude of the negativevoltage signal. In one preferred embodiment, the positive voltagegenerator 40 triples the voltage of the positive reference voltageprovided by the reference generator 75, and the negative voltagegenerator 44 doubles the negative reference voltage provided by thereference generator 75 so that the high voltage pulse has an effectivevoltage 5 times the magnitude of the reference voltages of the referencegenerator 75. Also, in one preferred embodiment, the positive voltagetimer 32 receives electrical power (via a signal path 79) having theincreased voltage from the positive voltage generator 40 so that thepositive voltage timer 32 can switch components in the positive voltagegenerator 40.

The advantage of using the positive voltage signal and the negativevoltage signal is that the cost of manufacturing the control circuit 12is reduced. That is, electrical components which switch over 18-20 Voltsare more expensive than electrical components which switch below 18-20Volts. By using the positive voltage signal and the negative voltagesignal with a magnitude less than or equal to 18-20 Volts (e.g. +18V and−12V), less expensive electrical components can be used to deliver aneffective voltage of over 18 Volts (e.g. 30V) to the shutter assembly14. Further, by providing the positive voltage signal and the negativevoltage signal to the shutter assembly 14 directly from the positivevoltage generator 40 and the negative voltage generator 44,respectively, use of a costly high voltage driver is not necessary. Forexample, a high voltage driver is described in more detail inapplicant's co-pending patent application identified by the U.S. Ser.No. 10/139,837, the entire contents of which is hereby incorporated byreference.

When the sensor output signal indicates to the weld detect circuit 28that an intense light, such as a welding arc, is present, the welddetect circuit 28 outputs a signal to the positive voltage timer 32 andthe negative voltage timer 36 via delay circuit 48 and signal paths 112and 116 to cause the positive voltage signal and the negative voltagesignal to be fed to the shutter assembly 14 via signal paths 88 and 92.That is, upon receipt of the signal from the weld detect circuit 28, thepositive voltage timer 32 and the negative voltage timer 36 outputrespective timing signals to the positive voltage generator 40 and thenegative voltage generator 44 via signal paths 96 and 100. In responsethereto, the positive voltage generator 40 outputs the positive voltagesignal to the shutter assembly 14 on the signal path 88, and thenegative voltage generator 44 outputs the negative voltage signal to theshutter assembly 14 on the signal path 92 to cause the shutter assembly14 to switch from the light state to the dark state. Then, the welddetect circuit 28 causes the positive voltage generator 40 and negativevoltage generator 44 to enable the stable AC waveform to the shutterassembly 14.

The stable AC waveform maintains the shutter assembly 14 in the darkstate. The stable AC waveform is preferably an essentially squarewaveform with a maximum of about +12 Volts to a minimum of about −12Volts. The stable AC waveform can be provided with other shapes, such asa sinusoidal shape, however, the efficiency of the circuit 12 will bereduced.

In one preferred embodiment, the stable AC waveform is produced asfollows. The oscillator circuit 52 provides an oscillating signal to theweld detect circuit 28 via a signal path 124 to cause the weld detectcircuit 28 to oscillate the output signals of the positive voltagegenerator 40 and the negative voltage generator 44 such that thepositive voltage generator 40 and the negative voltage generator 44synchronously output essentially AC waveforms, which are inverselyrelated, to the shutter assembly 14 via lines 88 and 92, respectively.Since the shutter assembly is not referenced to ground, as discussedabove, the shutter assembly 14 receives an effective square waveformwith a maximum equal to the difference between the maximum of the ACwaveform output by the positive voltage generator 40 and the minimum ofthe AC waveform output by the negative voltage generator 44, and with aminimum equal to the difference between the minimum of the AC waveformoutput by the positive voltage generator 40 and the maximum of the ACwaveform output by the negative voltage generator 44. For example, ifthe positive voltage generator 40 and the negative voltage generator 44output essentially inverse synchronous square waveforms with a maximumof +6 Volts and a minimum of −6 Volts to the shutter assembly 14 vialines 88 and 92, respectively, then the stable AC waveform received bythe shutter assembly 14 will effectively be a square waveform with amaximum of +12 Volts and a minimum of −12 Volts.

If the sensor output signal indicates to the weld detect circuit 28 thatno welding arc is present, the weld detect circuit 28 will cause a“light state” drive signal to be delivered to the shutter assembly 14via the delay circuit 48, the positive voltage generator 40, thenegative voltage generator 44, and the signal paths 112, 116, 92, and88. The delay circuit 48 delays the submission of the light state drivesignal to the positive voltage generator 40 and the negative voltagegenerator 44 for a predetermined time, thus preventing the shutterassembly 14 from switching to a light state during brief “off” periodsin the weld pulsations that exist with various weld types. Further, oncethe welding arc is extinguished, the work piece which is being weldedmay glow brightly for several milliseconds thereafter. The delay circuit48 delays the light state drive signal for desirably between about 0.1seconds to about 1 seconds, and more desirably between about 0.2 secondsto about 0.4 seconds so as to protect the individual's eyes from theglow from the work piece. The delay circuit 48 may have a fixed timedelay, or may be adjustable by a user so as to be set based on theuser's preference.

Referring now to FIG. 2, shown therein is a schematic diagram of onepreferred implementation of the control circuit 12. The sensor circuit24 includes one or more phototransistors (only two being shown forpurposes of clarity and labeled therein as S1 and S2). The output ofeach phototransistor S1 and S2 are coupled to a feedback circuit,labeled therein as 206 a and 206 b respectively. The construction andfunction of the phototransistors S1 and S2 are similar. Likewise, thefeedback circuits 206 a and 206 b are similar. Thus, only thephototransistor S1 and the feedback circuit 206 a will be discussedhereinafter in more detail for purposes of brevity.

Phototransistor S1 serves as the weld sensor. It receives an input ofincident light 220 and produces an output on line 208 representative ofthe intensity of the incident light. The phototransistor S1 used in thepresent invention is preferably a planar phototransistor configured fora surface mount. The planar phototransistor is smaller than conventionalmetal can phototransistors, thus allowing a reduction in size of theunit in which the sensor circuit is implemented. While the metal canphototransistors used in the sensor circuits of the prior art had athickness of about ½ inch, the planar phototransistors with a surfacemount used in the present invention have a thickness of only about1/16-⅛ inch. This reduction in thickness allows the sensor circuit 24 tobe implemented into a smaller and sleeker unit. Further, the surfacemount configuration of the phototransistor S1 allows the phototransistorto be easily affixed to a circuit board. The inventor herein has foundthat the TEMT4700 silicon npn phototransistor manufactured byVishay-Telefunken is an excellent phototransistor for the presentinvention as it has a smaller size than conventional metal canphototransistors and allows the sensor circuit to maintain a constantsignal level without excessive loading or the drawing of excessivecurrent.

The feedback circuit 206 a for the phototransistor S1 comprises aresistor capacitor circuit 216 connected between the emitter of thephototransistor S1 and ground, and a feedback transistor Q2 having abase coupled to line 218 of the resistor capacitor circuit 216, acollector coupled to the base of the phototransistor S1, and an emittercoupled to the ground via resistor R10. The resistor capacitor circuit216 and the feedback transistor Q2 in the phototransistor feedbackcircuit 206 a function to adjust the sensitivity of the phototransistorS1. The resistors R11 and R8 and capacitor C12 are chosen to be of asize to provide a relatively large time constant, and therefore arelatively slow response to changes in voltage on line 208. The delayexists because of the time it takes for the voltage on line 218 tocharge to an amount sufficiently large to activate transistor Q2.Exemplary values for resistors R11 and R8 are 2 M ohm and 1 M ohm,respectively. An exemplary value for capacitor C12 is 0.1 micro farads.A detailed description of the operation of the resistor capacitorcircuit 216 and feedback transistor Q2 can be found in prior U.S. Pat.Nos. 5,248,880 and 5,252,817, the disclosures of which have beenincorporated by reference.

The output of phototransistor S1 and feedback circuit 206 a is sent toline 208. A load resistor R6 is connected between line 208 and ground.In one embodiment, as shown for example in FIG. 2, line 208 is connectedto an OR logical circuit 224, which receives the outputs from thefeedback circuits 206 a and 206 b and permits the highest voltage levelfrom the feedback circuits 206 a and 206 b to be passed. In oneembodiment, the OR logical circuit 224 includes at least two diodes, asdesignated by the reference numeral D10. Further, the diodes D10 provideisolation between the feedback circuits 206 a and 206 b.

The output of the OR logical circuit 224 is coupled to line 209 via acapacitor C9. The capacitor C9 forms a filter to block the DC componentof the detected signal so that line 209 contains the DC blocked detectedsignal. The current on line 209 is diverted to ground via resistor R23.

Line 209 is connected to the noninverting input of an amplifier 210.Amplifier 210 is preferably configured as closed loop noninvertingamplifier wherein the resistors R3 and R9 form a feedback loop connectedto the inverting input of amplifier 210 as shown. Suitable values for R3and R9 have been found to be 390 K ohm and 1 M ohm, respectively. Theoutput of amplifier 210 on line 80 serves as the sensor circuit output.Line 80 is connected to the input of the weld detect circuit 28 via R14.

The solar power supply 64 of the power supply 16 powers thephototransistor S1 and amplifier 210 via line 68. Thus, if the solarpower supply 64 is left unexposed to incident light, phototransistor S1and amplifier 210 will not receive power, thus preventing thephototransistor S1 and amplifier 210 from draining the battery powersupply 60 when the welding helmet is not in use (when not in use, thewelding helmet is typically not exposed to intense light). The amplifier210 may be omitted in other applications or variations of this circuit.

The sensor circuit 24 operates in the presence of both AC welds and DCwelds. In an AC weld (also known as a MIG weld), the welding light ispulsating. Thus, the phototransistor S1 will detect a pulsating lightsignal. The frequency of the pulsations is often 120 Hz. In a DC weld(also known as a TIG weld), the welding light is substantiallycontinuous, with the exception of a small AC component. When an AC weldis present, the phototransistor will produce a pulsating output on line208. The variations in the voltage signal due to the pulses will bepassed through the capacitor C9 to line 209 and fed into the amplifier210. The amplifier 210 will then provide gain for the signal on line 209which is sufficient to trigger the delivery of the “dark state” drivesignal to the shutter assembly 14.

When a DC weld is present, the phototransistor S1 will quickly producean output on line 208 catching the rising edge of the DC weld. Thissudden rise in voltage on line 208 will be passed through to theamplifier 210 causing a signal on line 80 sufficient to trigger thedelivery of a “dark state” drive signal to the shutter assembly 14.Thereafter, capacitor C9 will block the DC component of the DC weld,allowing only the AC variations in the DC weld to pass through to theamplifier 210. A non-reactive element, e.g., resistor R20, is positionedin parallel with a filter circuit formed by capacitor C9, for example.The filter circuit can be a band-pass or a high-pass filter. Thenon-reactive element provides a DC bias to the input of the amplifier210 to aid in the detection of the DC weld. That is, the brighter thelight being generated from the weld becomes, the more sensitive thesensor circuit 24 becomes. In one embodiment, R20 can have a value of4.3 M ohm.

The output of the amplifier 210 is fed into the weld detect circuit 28.The weld detect circuit 28 is provided with an electronic switch, anexample of which is shown in FIG. 2 as the transistor Q3, a delaycircuit 230 and a switching circuit U3.

The delay circuit 230 can be formed of a RC circuit and serves toprevent inadvertent switching of the shutter assembly 14 from the darkstate to the light state. That is, the light received by the sensorcircuit 24 from the welding arc can be a pulsating signal caused bysputtering of the weld. When the amplifier 210 receives a signal ofsufficient magnitude, the output of the amplifier 210 goes high. Thehigh signal is fed to the gate of the transistor Q3. Transistor Q3 thenturns on and thereby shorts a capacitor C14 to ground. Once theintensity of the light detected by the sensor circuit 24 decreases,capacitor C14 will begin charging through R21 until the next pulse ofintense light is provided to the sensor circuit 24. Thus, the timeperiod of the RC circuit formed by the capacitor C14 and a resistor R21is selected to maintain the capacitor C14 in a “low” state betweenpulses to maintain a stable low signal to the switching circuit U3.

The “low” signal is provided to a switch input “A” of the switchingcircuit U3. This causes the X switch of the switching circuit U3 toswitch between the X1 and the X0 inputs. A high signal is applied to theX0 input and the ground reference is applied to the X1 input. Thus, whenthe low signal is provided to the switch input “A”, a high signal isprovided to the delay circuit 48 via switch X and the signal path 112.

The delay circuit 48 is provided with an electronic switch asrepresented by transistor Q8, and an RC circuit as represented by R28and C21. The high signal switches on the transistor Q8 causing thecapacitor C21 to charge. The delay circuit 48 provides a time delay whenthe control circuit 12 switches from the dark state to the light state.That is, when the welding stops the workpiece may still be glowingbrightly. Thus, the time delay of the delay circuit 48 is selected suchthat the user's eyes will be protected until the glow of the workpieceis diminished. The time delay of the delay circuit 48 can vary widelybased on user preference. However, suitable time periods range fromabout 0.2 seconds to about 0.4 seconds. Suitable values for the resistorR28 and the capacitor C21 are 4.3 M ohm and 0.047 micro farads,respectively.

The positive and negative voltage timers 32 and 36 serve to properlybias the inputs of the positive and negative voltage generators 40 and44 to generate the high voltage pulse. In one embodiment, the positivevoltage timer 32 is formed by resistors R29 and R27, transistor Q7, andcapacitors C22 and C16. The negative voltage timer 36 is formed byresistor R27 and capacitor C16. The weld detect circuit 28 triggers boththe positive voltage timer 32 and the negative voltage timer 36 suchthat the positive voltage signal and negative voltage signal aresynchronized. In the embodiment depicted in FIG. 2, the positive voltagesignal of the high voltage pulse is enabled for a different timeduration than the negative voltage signal. However, one of ordinaryskill in the art would recognize that the positive voltage timer and thenegative voltage timer can be embodied to cause the positive voltagesignal and the negative voltage signal to have essentially the same timeduration.

In the positive voltage timer 32 and negative voltage timer 36, theemitter of the transistor Q8 is connected to the capacitor C16 via line116. In the positive voltage timer 32, capacitor C16 is connected to thegate of transistor Q7. Transistor Q7 shorts the capacitor C22, which isconnected to switch inputs “A” and “B” of a switching circuit U5 of thepositive voltage generator 40. This causes the capacitor C22 to thenhave to recharge causing the time frame in which the positive voltagegenerator 40 produces the positive voltage signal of the high voltagepulse. In the negative voltage timer 36, the capacitor C16 is connectedto switch input “A” of switching circuit U4 of the negative voltagegenerator 44 and causes the negative voltage generator 44 to produce thenegative voltage signal of the high voltage pulse.

In one embodiment, the positive voltage generator 40 is provided with atleast two capacitors C18 and C19, and a directional control circuit 244.The switching circuit U5 of the positive voltage generator 40 has aplurality of switches X, Y and Z for switching the positive voltagegenerator 40 between a charging state and a discharging state. Each ofthe capacitors C18 and C19 are connected to the switching circuit U5 andthe positive reference voltage to establish charging of the capacitorsC18 and C19 in the charging state of the switching circuit U5.

Upon switch inputs “A” and “B” of switching circuit U5 receiving the lowsignal from the positive voltage timer 32, switches X and Y of switchingcircuit U5 switch to the discharging state. In the discharging state,the capacitors C18 and C19 are stacked to sum the voltage accumulated onthe capacitors. That is, a positive lead of the capacitor C18 isconnected to a negative lead of the capacitor C19 through the switch Y.The term “positive lead” means that there is a more positive charge onsuch lead as compared to the other lead. Likewise, the term “negativelead” means that there is a negative charge in reference to the otherlead. Assuming that the voltage reference is +6 Volts, this would causea +12 Volt potential to exist across the stacked capacitors C18 and C19.Further, the negative lead of the capacitor C18 is connected to thepositive reference voltage (e.g., +6V), through switch X so that thepositive voltage signal (e.g., +18 V) exists from the ground referenceto the positive lead of the capacitor C19.

The directional control circuit 244 permits the flow of current betweenthe positive leads of the capacitors C18 and C19 and the referencevoltage in the charging state of the switching circuit U5, and preventsthe flow of current between the positive leads of the capacitors C18 andC19 and the reference voltage in the discharging state of the switchingcircuit U5 so that the positive voltage signal is generated. Thepositive voltage signal is then provided to the shutter assembly 14 vialine 88 through the switch Z of switching circuit U5 of the positivevoltage generator 40.

As shown in FIG. 2, in one embodiment the directional control circuit244includes at least four diodes, as designated by the reference numeral D8and D9. Although the directional control circuit 244 has been shown anddescribed as the diodes D8 and D9, it should be understood that thedirectional control circuit 244 could be implemented in other manners.For example, the directional control circuit 244 can be implemented asany device having a P-N junction, such as a transistor, or an enhancedMOSFET.

The value of capacitors C18 and C19 can vary widely depending on the 1)output voltage, 2) load, and 3) length of time for the voltage to switchthe shutter assembly 14. For example, in one embodiment the capacitorsC18 and C19 can be 2.2 micro farad capacitors. The switching circuit U5is preferably 1) an integrated circuit having a plurality ofelectronically controlled switches, or 2) separate electronicallycontrolled switches.

The negative voltage generator 44 is constructed in a similar manner asthe positive voltage generator 40, except as discussed hereinafter. Inthe charging state, the positive lead of capacitor C20 is connected toground and the negative lead of capacitor C20 is connected to thenegative reference voltage. Assuming that the negative reference voltageis −6 Volts, this would cause a −6 Volt potential to exist across thecapacitor C20. In the discharging state, the positive lead of thecapacitor C20 is connected to the negative reference voltage (e.g., −6V) through the switch X so that the negative voltage signal (e.g., −12V) exists from the ground reference to the negative lead of thecapacitor C20. The negative voltage signal is output to the shutterassembly 14 via line 92 through switch Y and switch Z of switchingcircuit U4 of the negative voltage generator 44. The negative voltagegenerator 44 is also provided with a directional control circuit 250permitting the flow of current between the negative lead of capacitorC20 and the negative reference voltage in the charging state of theswitching circuit U4, and preventing the flow of current between thenegative lead of the capacitor C20 and the reference voltage in thedischarging state of the switching circuit U4 so that the negativevoltage signal is generated.

It should be understood that the description set forth above describes apreferred embodiment of the present invention. Changes can be madewithout departing from the scope of the invention. For example, thecapacitor C18 and/or the capacitor C19 of the positive voltage generator40 do not have to be connected to the positive reference voltage in thecharging state and/or discharging state. Any voltage, including thepositive reference voltage and/or negative reference voltage, can beused so long as the capacitors C18 and C19 are charged and discharged asdescribed herein to provide the positive voltage signal of the highvoltage pulse. Further, the capacitors C18 and C19 do not have to beconnected to the same voltage. Likewise, capacitor C20 of the negativevoltage generator 44 does not have to be connected to the negativereference voltage in the charging and/or discharging state. Any voltage,including the positive reference voltage and/or negative referencevoltage, can be used so long as capacitor C20 is charged and dischargedas described herein to provide the negative voltage signal of the highvoltage pulse. Furthermore, it should be understood that more capacitorsand/or other energy storage devices can be used to construct thepositive voltage generator 40 and/or negative voltage generator 44 ofthe present invention.

For example, the capacitors C18 and C19 of the positive voltagegenerator 40 can be connected to a first voltage to establish chargingof the capacitors C18 and C19 in the charging state, and the capacitorC18 can be connected to a second voltage in the discharging state. Thesecond voltage connected to capacitor C18 in the discharging state canbe at the same or a different voltage level as the first voltageconnected to capacitors C18 and C19 in the charging state. Likewise,capacitor C20 of the negative voltage generator 44 can be connected to afirst voltage to charge capacitor C20 in the charging state, andconnected to a second voltage in the discharging state. The secondvoltage connected to the capacitor C20 in the discharging state can beat the same or a different voltage level as the first voltage connectedto capacitor C20 in the charging state.

When the capacitor C22 has recharged, a high signal is output to thepositive voltage generator 40 via the line 96. The high signal switchesthe switching circuit U5 from the discharging state to the chargingstate to turn off the positive voltage signal. The switching circuit U4,after receiving the high signal from C16 returns to receiving a lowsignal and switches from the discharging state to the charging state toturn off the negative voltage signal.

Once the positive and negative voltage signals have been turned off, thestable AC waveform, as discussed above, is provided to the shutterassembly 14 through the oscillator circuit 52 and the switching circuitsU3, U5, and U4 via lines 124, 254, 88 and 92. Since the switchingcircuits U3, U5, and U4 of the weld detect circuit 28, the positivevoltage generator 40, and the negative voltage generator 44,respectively, are used to provide the stable AC waveform to the shutterassembly 14, a separate circuit is not necessary to generate the stableAC waveform or to deliver the stable AC waveform to the shutter assembly14 after the high voltage pulse has been delivered to the shutterassembly 14. However, one of ordinary skill in the art would recognizethat the control circuit 12 could be provided with a separate deliverycircuit to deliver the high voltage pulse and/or the stable AC waveformto the shutter assembly 14, such as for example shown in co-pendingpatent application U.S. Ser. No. 10/139,837, the entire contents ofwhich are incorporated herein by reference.

The stable AC waveform is produced as follows. The oscillating circuit52 provides an oscillating signal to the Z1 input of the switchingcircuit U3 of the weld detect circuit 28 via line 124, which is thenoutput to switch input “C” of switching circuit U5 via switch Z ofswitching circuit U3 and line 254. This causes switch Z of switchingcircuit U5 of the positive voltage generator 40 to oscillate between theZ0 and Z1 inputs. Since switching circuit U5 is at the charging state,Z0 will be the charged potential across C19, which is the positivereference voltage (e.g. +6 V), as discussed above. The Z1 input ofswitching circuit U5 is connected to a reference voltage of oppositepolarity (e.g. −6V) through switch Y of the switching circuit U3. Assuch, the oscillating signal causes the switching circuit U5 of thepositive voltage generator 40 to periodically switch the polarity of thesignal transmitted to the shutter assembly 14 via line 88 so as toeffectively deliver a square waveform (e.g. with a maximum of +6V and aminimum of −6V).

The oscillating signal input to Z1 of switching circuit U3 is alsooutput via switch Z of switching circuit U3 to the switch input “B” ofswitching circuit U4 of the negative voltage generator 44, therebycausing switch Y of switching circuit U4 to oscillate between Y0 and Y1.Switch Y of switching circuit U4 is connected to Z1 of switching circuitU4 so that when switch input “C” of switching circuit U4 is high, theswitch Z of switching circuit U4 oscillates between Y0 and Y1. Sinceswitching circuit U4 is at the charging state, Y0 will be the chargedpotential across C20, which is the negative reference voltage (e.g.−6V), as discussed above. Y1 is connected to a reference voltage ofopposite polarity (e.g. +6V) and, as such, the oscillating signal causesthe switching circuit U4 of the negative voltage generator 44 toperiodically switch the polarity of the signal transmitted to the signaltransmitted to the shutter assembly 14 via line 92 so as to effectivelydeliver a square waveform (e.g. with a maximum of +6V and a minimum of−6V) which is inversely synchronized with the square waveform providedby the positive voltage generator 40 via line 88.

Since the square waveforms produced by switching circuits U5 and U4 areinversely synchronized, the AC waveform received by the shutter assembly14, which is not referenced to ground, is effectively a square waveformwhich has a maximum equal to the difference between the maximum of thesquare waveform output by the positive voltage generator 40 and theminimum of the square waveform output by the negative voltage generator44 (e.g., max=+6V−(−6V)=+12V), and a minimum equal to the differencebetween the minimum of the square waveform output by the positivevoltage generator 40 and the maximum of the square waveform output bythe negative voltage generator 44 (e.g., min=−6V−6V=−12V).

When the sensor circuit 24 no longer senses the welding arc, the signalon line 112 switches to a “low” state, thereby turning off thetransistor Q8. This permits the capacitor C21 to discharge through theresistor R28 causing a low state signal to be delivered on the line 116after a predetermined time period. The low state signal is received bythe switch input “C” of the switching circuit U4 and by the switch input“C” of the switching circuit U3 which thereby causes a “low” statesignal to be output to the switch input “C” of switching circuit U5 viaswitch Z of the switching circuit U3. As a result, switching circuit U5and U4 output the same reference voltage (e.g. +6V), thereby causing theshutter assembly 14 to switch from the dark state to the light state.

Referring now to FIG. 3, shown in schematic diagram form is anotherimplementation of a weld detect circuit (labeled therein as 28 a), apositive voltage generator (labeled therein as 40 a), and a negativevoltage generator (labeled therein as 44 a). The weld detect circuit 28a, the positive voltage generator 40 a, and the negative voltagegenerator 44 a depicted in FIG. 3 are similar in construction andfunction to the weld detect circuit 28, the positive voltage generator40, and the negative voltage generator 44, respectively, as discussedabove with reference to FIG. 2, except that the weld detect circuit 28a, the positive voltage generator 40 a, and the negative voltagegenerator 44 a are constructed so as to reduce the “bleeding-off” ofcharge from the capacitors by the diodes, and to reduce fluctuations inthe dark state drive signal caused by voltage drops across the diodes.Therefore, for purposes of brevity, similar components of the welddetect circuit 28 a, the positive voltage generator 40 a, and thenegative voltage generator 44 a are labeled in FIG. 3 with the samenumber prefix, but with an additional alphanumeric suffix “a”, as thecomponents of the weld detect circuit 28, the positive voltage generator40, and the negative voltage generator 44 depicted in FIG. 2. Further,for purposes of brevity, only the differences in operation of the welddetect circuit 28 a, the positive voltage generator 40 a, and thenegative voltage generator 44 a are discussed in further detail below.

The output of the positive voltage timer 32 at capacitor C22 isconnected to switch inputs “A” and “C” of a switching circuit U5 a ofthe positive voltage generator 40 a to cause the positive voltagegenerator 40 a to produce the positive voltage of the high voltagepulse. The output of the negative voltage timer 36 at capacitor C16 isconnected to switch inputs “A” and “C” of a switching circuit U4 a ofthe negative voltage generator 44 a to cause the negative voltagegenerator 44 a to produce the negative voltage signal of the highvoltage pulse.

The positive voltage generator 40 a is provided with one capacitor C19 aand a directional control circuit 244 a. The capacitor C19 a of thepositive voltage generator 40 a functions similarly to the capacitorsC18 and C19 of the positive voltage generator 40 discussed withreference to FIG. 2. The capacitor C19 a of the positive voltagegenerator 40 a has a high capacitance, e.g. 4.7 micro farads. During thecharging state, the capacitor C19 a is charged with reference to thepositive reference voltage and the negative reference voltage via switchX of switching circuit U5 a so as to effectively connect capacitor C19 ato a voltage having a magnitude of the difference between the positivereference voltage and the negative reference voltage across thecapacitor C19 a. Assuming that the positive reference voltage is +6Volts and the negative reference voltage is −6 Volts, this would cause apotential with a magnitude of 12 Volts to exist across the capacitor C19a in the charging state of switching circuit U5 a.

In the discharging state, upon switch inputs “A” and “C” of switchingcircuit U5 a receiving the low signal from the positive voltage timer32, switches X and Z of switching circuit U5 a switch so that a positivelead of the capacitor C19 a is connected to line 88 via switch Z, and anegative lead of the capacitor C19 a is connected to the positivereference voltage (e.g., +6V) via switch X. As a result, the positivevoltage signal (e.g., +18V) exists from the ground reference to thepositive lead of the capacitor C19 a. Additionally, to reduce noise, thepositive voltage generator 40 a can further include a capacitor C24connected between the positive lead of the capacitor C19 a and ground,such as shown for example in FIG. 3.

The directional control circuit 244 a, in one embodiment, includes atleast two diodes, as designated in FIG. 3 by the reference numeral D8 a.The directional control circuit 244 a permits the flow of currentbetween the positive lead of the capacitor C19 a and the referencevoltage in the charging state of the switching circuit U5, and preventsthe flow of current between the positive lead of the capacitor C19 a inthe discharging state of the switching circuit U5 so that the positivevoltage signal is generated. The positive voltage signal is provided tothe shutter assembly 14 via line 88 through switch Z of switchingcircuit U5 a of the positive voltage generator 40 a.

In the negative voltage generator 44 a, in the charging state, apositive lead of a capacitor C20 a is connected to ground and a negativelead of capacitor C20 a is connected to a negative reference voltage.Assuming that the negative reference voltage is −6 Volts, this wouldcause a −6 Volt potential to exist across the capacitor C20 a. In thedischarging state, the positive lead of the capacitor C20 a is connectedto the negative reference voltage (e.g., −6V) through the switch X ofswitching circuit U4 a so that the negative voltage signal (e.g., −12V)exists from the ground reference to the negative lead of the capacitorC20 a. Additionally, to reduce noise, the negative voltage generator 44a can further include a capacitor C25 connected between the negativelead of capacitor C20 a and ground, such as shown for example in FIG. 3.

The negative voltage generator 44 a is also provided with a directionalcontrol circuit 250 a, which in one embodiment includes one diode, asdesignated in FIG. 3 by the reference numeral D5 a. The directionalcontrol circuit 250 a permits the flow of current between the negativelead of the capacitor C20 a and the negative reference voltage in thecharging state of the switching circuit U4 a, and prevents the flow ofcurrent between the negative lead of the capacitor C20 a and thereference voltage in the discharging state of the switching circuit U4 aso that the negative voltage signal is generated. The negative voltagesignal is outputted to the shutter assembly 14 via line 92 throughswitch Z of switching circuit U4 a of the negative voltage generator 44a.

It should be understood that the description set forth above describes apreferred embodiment of the present invention. Changes can be madewithout departing from the scope of the invention. For example, thecapacitor C19 a of the positive voltage generator 40 a does not have tobe connected to the positive reference voltage and/or the negativereference voltage in the charging state and/or discharging state. Anyvoltages, including the positive reference voltage and/or negativereference voltage, can be used so long as the capacitor C19 a is chargedand discharged as described herein to provide the positive voltagesignal of the high voltage pulse. Likewise, capacitor C20 a of thenegative voltage generator 44 a does not have to be connected to thenegative reference voltage in the charging and/or discharging state. Anyvoltage, including the positive reference voltage and/or negativereference voltage, can be used so long as capacitor C20 a is charged anddischarged as described herein to provide the negative voltage signal ofthe high voltage pulse. Furthermore, it should be understood that morecapacitors and/or other energy storage devices can be used to constructthe positive voltage generator 40 a and/or negative voltage generator 44a of the present invention.

For example, the capacitor C19 a of the positive voltage generator 40 acan be connected to a first voltage to establish charging of thecapacitor C19 a in the charging state, and the capacitor C19 a can beconnected to a second voltage in the discharging state. The secondvoltage level connected to capacitor C19 a in the discharging state canbe at the same or a different voltage level as the first voltageconnected to capacitor C19 a in the charging state. Likewise, capacitorC20 a of the negative voltage generator 44 a can be connected to a firstvoltage to charge capacitor C20 a in the charging state and connected toa second voltage in the discharging state. The second voltage connectedto capacitor C20 a in the discharging state can be at the same or adifferent voltage level as the first voltage connected to the capacitorC20 a in the charging state.

When the capacitor C22 of the positive voltage timer 32 has recharged, ahigh signal is outputted to the positive voltage generator 40 a via theline 96. The high signal switches the switching circuit U5 a from thedischarging state to the charging state to turn off the positive voltagesignal. The switching circuit U4 of the negative voltage generator 44 a,after receiving the high signal from capacitor C16 of the negativevoltage timer 36, returns to receiving a low signal and switches fromthe discharging state to the charging state to turn off the negativevoltage signal.

Once the positive and negative voltage signals have been turned off, thestable AC waveform is provided to the shutter assembly 14 through theoscillator circuit 52 and the switching circuits U3 a, U5 a, and U4 avia lines 124, 254, 88 and 92. The stable AC waveform is produced asfollows.

The oscillating circuit 52 a provides an oscillating signal to switchinput “B” of the switching circuit U3 a of the weld detect circuit 28 avia line 124. This causes switch Y of switching circuit U3 a of the welddetect circuit 28 a to oscillate between Y0 and Y1 inputs. Y1 isconnected to the negative reference voltage (e.g. −6V) and Y0 isconnected to a reference voltage of opposite polarity (e.g. +6V) viaswitch Y of switching circuit U5 a.

The output of switch Y of switching circuit U3 a is connected to the Z1input of switching circuit U5 a. When switch input “C” of switchingcircuit U5 a is high, the output of switch Z of switching circuit U5 aoscillates between Y0 and Y1, i.e. the output of switch Z of switchingcircuit U5 a of the positive voltage generator 40 a will transmit asignal which periodically switches in polarity to the shutter assembly14 via line 88 so as to effectively deliver a square waveform (e.g. witha maximum of +6V and a minimum of −6V).

The oscillating signal is also output via line 124 to the switch input“B” of switching circuit U4 a of the negative voltage generator 44 a,thereby causing the output of switch Y of switching circuit U4 a tooscillate between Y0 and Y1. The output of switch Y of switching circuitU4 a is connected to Z0 switching circuit U4 a so that when switch input“C” of switching circuit U4 a is low, the output of switch Z ofswitching circuit U4 a oscillates between Y0 and Y1. Y0 is connected tothe negative reference voltage (e.g. −6V) and Y1 is connected to areference voltage of opposite polarity (e.g. +6V) via switch Y ofswitching circuit U5 a. As such, the output of switch Z of switchingcircuit U4 a of the negative voltage generator 40 a will transmit asignal which periodically switches in polarity to the shutter assembly14 via line 92 so as to effectively deliver a square waveform (e.g. witha maximum of +6V and a minimum of −6V) which is inversely synchronizedwith the square waveform provided by the positive voltage generator 40 avia line 88.

Since the square waveforms outputted by switching circuits U5 a and U4 aare inversely synchronized, the AC waveform received by the shutterassembly 14, which is not referenced to ground, is effectively a squarewaveform which has a maximum equal to the difference between the maximumof the square waveform output by the positive voltage generator 40 a andthe minimum of the square waveform output by the negative voltagegenerator 44 a (e.g., max=+6V−(−6V)=+12V), and a minimum equal to thedifference between the minimum of the square waveform output by thepositive voltage generator 40 a and the maximum of the square waveformoutput by the negative voltage generator 44 a (e.g., min=−6V −6V=−12V).

When the sensor circuit 24 no longer senses the welding arc, the signalon line 112 switches to a “low” state, thereby turning off thetransistor Q8 and causing the capacitor C21 to discharge through theresistor R28 and switch line 116 to a low state after a predeterminedtime period. The low state signal on line 116 is received by the switchinput “B” of the switching circuit U5 a, which thereby causes switch Yof switching circuit U5 a to output the signal on the Y0 input, which isconnected to the negative reference voltage (e.g. −6V) via switch Z ofswitching circuit U3 a. The negative reference voltage is outputted fromswitch Y of switching circuit U5 a to line 88 via switch Y of switchingcircuit U3 a and switch Z of switching circuit U5 a. The negativereference voltage is also outputted from switch Y of switching circuitU5 a to line 92 via switch Y and switch Z of switching circuit U4 a. Asa result, switching circuit U5 a of the positive voltage generator 40 aand switching circuit U4 a of the negative voltage generator 44 a outputthe same voltage (e.g. −6V), thereby causing the shutter assembly 14 toswitch from the dark state to the light state.

Referring now to FIG. 5, shown therein is a front perspective view ofthe eye protection device 10. The sensor circuit 24 of the eyeprotection device 10 includes a pair of spatially disposed lightdetectors, such as phototransistors S1 and S2, for sensing the weldingarc.

The eye protection device 10 can be provided with a plurality ofcontrols for controlling various settings thereof. For example, the eyeprotection device 10 can be provided with a knob (not shown) or othercontrol mechanism, such as one or more buttons, connected to anysuitable component for adjusting the settings, e.g., sensitivity, delay,or shade, of the eye protection device 10.

FIG. 6 is a rear perspective view of the eye protection device 10. FIG.7 is a front elevational view of the eye protection device 10. FIG. 8 isa side elevational view of the eye protection device 10. FIG. 9 is afront elevational view of the eye protection device 10.

One skilled in the art will recognize that the present invention issusceptible to numerous modifications and variations. For example, theshutter assembly 14 and the control circuit 12 can be implemented in acassette connectable to a welding helmet, or integrated into the weldinghelmet. Further, the user controls can be on the cassette or separatefrom the cassette. For example, the user controls can be implemented asa “pig-tail.”

The embodiments of the invention discussed herein are intended to beillustrative and not limiting. Other embodiments of the invention willbe obvious to those skilled in the art in view of the above disclosure.Changes may be made in the embodiments of the invention describedherein, or in the parts or the elements of the embodiments describedherein, or in the steps or sequence of steps of the methods describedherein, without departing from the spirit and/or the scope of theinvention.

1. An auto darkening eye protection device comprising: a shutterassembly adjustable between a light state and a dark state; and acontrol circuit comprising: a power supply having a voltage; a sensingcircuit sensing an occurrence of a welding arc and providing an outputindicative of the occurrence of the welding arc; a weld detect circuitreceiving the output of the sensing circuit, the weld detect circuitenabling a high voltage pulse and a stable AC waveform to be deliveredto the shutter assembly; and a positive voltage generator and a negativevoltage generator receiving power from the power supply and cooperatingto output the high voltage pulse and the stable AC waveform to theshutter assembly to switch the shutter assembly from the light state tothe dark state upon enablement by the weld detect circuit, wherein thepositive voltage generator and the negative voltage generator arecoupled to the shutter assembly such that the stable AC waveformdirectly passes from the positive voltage generator and the negativevoltage generator to the shutter assembly.
 2. The auto darkening eyeprotection device of claim 1, wherein the positive voltage generator andthe negative generator are coupled to the shutter assembly such that theoutput of the positive voltage generator and the negative generatorpasses to the shutter assembly without passing through a high voltagedriver.
 3. The auto darkening eye protection device of claim 1, whereinthe positive voltage generator produces a positive voltage signal andthe negative voltage generator produces a negative voltage signal andwherein the positive and negative voltage signals are each referenced toground.
 4. The auto darkening eye protection device of claim 1, whereinthe high voltage pulse has a voltage in a range from about 15 Volts toabout 120 Volts, and a time period from about 10 microseconds to about100 milliseconds.
 5. The auto darkening eye protection device of claim3, wherein the leading edges of the positive and negative voltagesignals are synchronized.
 6. The auto darkening eye protection device ofclaim 1, wherein the positive voltage generator includes: a switchingcircuit having a charging state and a discharging state; at least twocapacitors, each of the capacitors connected to the switching circuitand a first voltage to establish charging of the capacitors in thecharging state of the switching circuit, and a negative lead of one ofthe capacitors electrically connected to a positive lead of another oneof the capacitors and a negative lead of another one of the capacitorselectrically connected to a second voltage in the discharging state ofthe switching circuit; and a directional control circuit connected tothe capacitors to permit the flow of current between the positive leadsof the capacitors and the first voltage in the charging state of theswitching circuit, and to prevent the flow of current between thepositive leads of the capacitors and the first voltage in thedischarging state of the switching circuit.
 7. The auto darkening eyeprotection device of claim 6, wherein the directional control circuit ofthe positive voltage generator includes at least four diodes.
 8. Theauto darkening eye protection device of claim 6, wherein the switchingcircuit of the positive voltage generator operates at voltage levelswith a magnitude of no greater than 20 Volts.
 9. The auto darkening eyeprotection device of claim 1, wherein the positive voltage generatorincludes: a switching circuit having a charging state and a dischargingstate; at least one capacitor connected to the switching circuit and afirst voltage to establish charging of the capacitor in the chargingstate of the switching circuit, and a negative lead of the capacitorelectrically connected to a second voltage in the discharging state ofthe switching circuit; and a directional control circuit connected tothe capacitor to permit the flow of current between the positive lead ofthe capacitor and the first voltage in the charging state of theswitching circuit, and to prevent the flow of current between thepositive lead of the capacitor and the first voltage in the dischargingstate of the switching circuit.
 10. The auto darkening eye protectiondevice of claim 9, wherein the directional control circuit of thepositive voltage generator includes at least two diodes.
 11. The autodarkening eye protection device of claim 9, wherein the switchingcircuit of the positive voltage generator operates at voltage levelswith a magnitude of no greater than 20 Volts.
 12. The auto darkening eyeprotection device of claim 1, wherein the negative voltage generatorincludes: a switching circuit having a charging state and a dischargingstate; at least one capacitor, the capacitor connected to the switchingcircuit and a first voltage to establish charging of the capacitor inthe charging state of the switching circuit, and a positive lead of thecapacitor electrically connected to a second voltage in the dischargingstate of the switching circuit; and a directional control circuitconnected to the capacitor to permit the flow of current between thenegative lead of the capacitor and the first voltage in the chargingstate of the switching circuit, and to prevent the flow of currentbetween the negative lead of the capacitor and the first voltage in thedischarging state of the switching circuit.
 13. The auto darkening eyeprotection device of claim 12, wherein the directional control circuitof the negative voltage generator includes at least one diode.
 14. Theauto darkening eye protection device of claim 13, wherein the switchingcircuit of the negative voltage generator operates at voltage levelswith a magnitude of no greater than 20 Volts.